Pilot Study: Identification of the T Cell Tumor Microenvironment of Premalignant and Malignant Anal Lesions.

Background: Anal squamous cell cancer incidence has risen 2.2% each year over the past decade. Current screening includes anal cytology and high-resolution anoscopy but is burdened with sampling error and patient discomfort.

Objective: Analyze the T cell microenvironment of normal, premalignant, including low- and high-grade squamous intraepithelial lesions, and cancer.

Design: IRB-approved prospective study of patients with anal dysplasia and cancer. Normal, dysplastic and/or cancer tissue are obtained from patients. Tissue is digested to obtain a single cell suspension. Flow cytometry analysis is performed on matched patient samples to evaluate T cell biomarkers.

Settings: A single tertiary-care academic center.

Patients: Over the age of 18 and scheduled to undergo high resolution anoscopy, examination under anesthesia, or abdominoperineal resection.

Main outcome measures: Descriptive statistics are utilized to understand differences in the tumor microenvironment of normal, premalignant, and malignant tissue.

Results: Twenty patients underwent immunophenotyping. Normal tissue was characterized by the presence of few infiltrating lymphocytes. Anal cancers contained 30-50% regulatory T cells, which were infrequent in dysplasia. In anal cancer, conventional CD4+ T cells expressed high levels of ICOS and PD-1, reflective of tumor antigen recognition. In premalignant lesions, CD4+ conventional T cells also expressed ICOS and PD-1 but lacked coexpression of chronic activation and proliferation markers. CD8+ T cells with a CD103+CD39+ phenotype, indicative of chronic stimulation and tissue residency, were increased in anal cancer.

Limitations: This study is limited by its small sample size. Results may not be generalizable to a larger population.

Conclusions: The data demonstrates that T cell infiltrates differ between normal, premalignant, and malignant lesions - with tissue from anal squamous cell cancer containing activated, chronically stimulated T cells. Future clinical diagnostic technology would yield a T cell pathological footprint to differentiate between premalignant and malignant lesions, in addition to the creation of a less invasive serum T cell biomarker test. See Video Abstract.